Clinical performance of bonded leucite-reinforced glass ceramic inlays and onlays after eight years

Objective: Ceramic inlays and onlays are a tooth colored alternative to metallic restorations. Clinical long-term data are scarce though, especially about inlays and onlays having proximal margins in dentin. The present prospective controlled clinical study evaluated the clinical performance of IPS Empress inlays and onlays with cuspal replacements and proximal margins below the cementoenamel junction over eight years. Methods: Ninety six ceramic restorations were placed in 34 patients by six dentists. The restorations were bonded with an enamel/dentin bonding system (Syntac Classic) and four different resin composite systems. The restorations were assessed after placement by two calibrated investigators using modified USPHS codes and criteria at the following time periods: baseline, 1,2,4,6 and 8 years. Results: Eight of the 96 restorations investigated had to be replaced (failure rate 8%; Kaplan–Meier): Six inlays suffered cohesive bulk fractures, two teeth required endodontic treatment. After eight years of clinical service, significant deterioration (Friedman 2-way ANOVA; P<0.05) was found for marginal adaptation of the remaining restorations. 98% of the surviving restorations exhibited marginal deficiencies, independent of the luting composite. Conclusions: IPS Empress inlays and onlays demonstrated to be successful even in large defects. Neither the absence of enamel margins, nor cuspal replacement significantly affected the quality of the restorations.